On Thursday, three men aged 43, 39 and 27 were arrested and a quantity of heroin seized when specialist detectives from the PSNI’s organised crime unit swooped on a flat in north Belfast.

In a separate raid at a terraced house in the east of the city, police found up to 10 mobile phones and drugs-related paraphernalia including a large quantity of plastic inners from children’s chocolate eggs used by smugglers to conceal narcotics internally.

If caught, those involved in the sale and supply of heroin can expect to serve lengthy jail sentences, police have warned.

DI Dunlop added: “Heroin can kill - that is a fact - and anyone who is suspected of involvement in the supply of this drug can expect to be arrested by police and presented before the courts.

“Those who deal in this kind of drug should be aware that, upon conviction, the supply of any class A drug will attract a lengthy prison sentence.”

Wraps containing 0.15 grams of heroin, often adulterated with over the counter painkillers such as paracetamol or bulked out with talcum powder and even brick dust, are being sold on street corners for about £20.

In Belfast, dealers frequently traverse the city on bicycles to deliver the Class A drug - much of which is brought in from the Republic.

Others use electronic lockers outside well known supermarkets to take receipt of larger packages of illegal drugs ordered online.

DI Dunlop said: “It gets in through various routes. It can come in through the post. It can come in on the back of a truck. It can come in on a bus or a car up from Dublin

“(There are) various modes of transport and methods of importation.”

Heroin is a drug made from morphine, which is extracted from the opium poppy. It can be injected intravenously, smoked or snorted.

Street names include “H”, “brown”, “smack” or “skag”.

The PSNI has said there is no evidence or intelligence linking paramilitaries to the sale of heroin, but a number of organised crime gangs, with links outside the UK, are believed to be involved.

Last month, the PSNI and National Crime Agency (NCA) seized heroin with an estimated street value of £14,000 in Co Down.

A heroin dealing den being run from underneath a bridge in East Belfast was also recently exposed.

Vulnerable addicts are often exploited by crime masters and are forced to sell heroin to feed their own habit.

DI Dunlop said: “We have reason to believe that a lot of the street dealers around greater Belfast and elsewhere in Northern Ireland may themselves be users.

“Obviously they are vulnerable individuals being exploited. Clearly they are committing crime as well, but we are trying to prevent the harm, protect people and keep people safe by taking this heroin off the streets.”

According to the latest figures from the PSNI, there were 5,025 drug seizures and 2,944 drug-related arrests over the past year - an increase on the 4,894 seizures and 2,774 arrests for the same period during the previous year.